This application is related to Japanese Patent Application No. H11-238784, filed on Aug. 25, 1999, the disclosure of which is hereby incorporated by reference in its entirety.
The present invention relates to a pretensioner that is built into a seatbelt device for restraining passengers to the seats of vehicles and the like, for rotating the take-up shaft for a seatbelt in the take-up direction in an emergency. More particularly, the present invention relates to a pretensioner with improved safety, wherein gas is allowed to escape in the event that the internal gas pressure rises excessively and there are decreased adverse effects on other equipment.
In recent years, an increasing number of seatbelt devices with pretensioners have been provided to vehicles, principally automobiles. A pretensioner is for instantaneously rotating the reel (take-up shaft) on which the seatbelt is wound in the take-up direction in the event of a vehicle collision, thereby taking up the slack in the belt and providing the belt with tension. The device driving this pretensioner generally ignites gunpowder according to a detection signal emitted at the time of collision of the vehicle, and drives a reel rotating mechanism by gas pressure generated by the explosion of gunpowder. A conventional example of such a pretensioner is the pretensioner disclosed in DE19545795-C1 (97-166921/16) or U.S. Pat. No. 5,875,634, for example. FIG. 17(A) is a perspective view illustrating the configuration of the pipe base portion of the above pretensioner, and FIG. 17(B) is a frontal cross-section view of the same part.
This pretensioner has a pipe 110. An attachment portion 111 is formed at the end of the pipe 110. This attachment portion 111 is formed so as to be somewhat greater in diameter than the pipe 110. A sleeve 114 is fixed at the inner side of the attachment portion 111. A gas generator 113 is stored within the sleeve 114. Further, a hole 115 is formed to the side wall of the attachment portion 111.
The gas generator 113 explodes in response to the signal at the time of collision of the vehicle, and discharges high-pressure gas within the pipe 110. The belt take-up mechanism is driven by the energy of this gas. Now, in the event that abnormal pressure exceeding the normal operating pressure occurs within the pipe 110, the interior portion of the hole 115 bursts, and the gas pressure of the gas generator 113 blows out of here. Thus, generation of dangerously high pressure within the pipe 110 can be prevented.
However, with the above conventional pretensioner, the position at which to form the hole 115 from which gas pressure blows out is restricted to a narrow range on the side wall of the attachment portion 111. Accordingly, the layout for dealing with blowout of gas and flames is difficult.
The present invention has been made in light of the above problems, and it is an object thereof to provide a pretensioner with improved safety, wherein gas is allowed to escape appropriately in the event that the internal gas pressure rises excessively, thus improving safety of the device even further.
In order to solve the above problems, the pretensioner according to a first embodiment of the present invention is a pretensioner for rotating the take-up shaft of a seatbelt in the take-up direction in the event of an emergency to provide the belt with pretension, comprising: a gas generator; a driving member accelerated by the gas generated by the gas generator; a path for storing and guiding the driving member; a channel for guiding the gas to the path; means for converting the motion of the accelerated driving member into force for rotating the take-up shaft; and gas bypass means for discharging the gas out from the channel in the event that internal pressure exceeding a certain pressure (i.e., abnormal pressure) is applied to the channel; wherein the gas bypass means includes a hole provided to the side wall of the channel, and a plugging material which normally plugs off the hole. With the pretensioner according to the first embodiment of the present invention, the plugging material may be a rivet.
With this embodiment of the present invention, in the event that there is internal pressure exceeding a certain pressure (i.e., abnormal pressure) in the channel, the plugging member blows out under this abnormal pressure and the hole opens, so gas escapes from this hole. Accordingly, excessively great pressure can be prevented from occurring within the channel. In this case, there is the advantage that the gas escaping means can be configured in an inexpensive and simple manner.
Also, with the pretensioner according to the first embodiment of the present invention, two holes may be provided opposing the cross-sectional radial direction of the channel, with the plugging material being a through rivet plugging both holes.
In this case there is the advantage that the work of attaching the rivet to the channel can be carried out easily. Also, the hole boring for the channel can be performed by a punching process of a through hole, which is easier.
Further, with the pretensioner according to the first embodiment of the present invention, an O-ring may be introduced between the outer surface of the channel and the end of the rivet. In this case, the gap between the hole and rivet is sealed by the O-ring. Accordingly, there is less gas leakage under normal pressure.
Also, with the pretensioner according to the first embodiment of the present invention, the plugging member may be a resin cap having an air hole; wherein the resin cap is arranged such that the air hole is plugged in the event that the internal pressure of the channel is the normal gas generator generating pressure; and wherein the resin cap detaches from the channel in the event that the internal pressure within the channel is an abnormal pressure. In this case, the air hole is released in the event that pressure decreases following operation, thereby preventing pressure from remaining within the channel.
The pretensioner according to a second embodiment of the present invention is a pretensioner for rotating the take-up shaft of a seatbelt in the take-up direction in the event of an emergency to provide the belt with pretension, the pretensioner comprising: a gas generator; a driving member accelerated by the gas generated by the gas generator; a path for storing and guiding the driving member; a channel for guiding the gas to the path; means for converting the motion of the accelerated driving member into force for rotating the take-up shaft; and gas bypass means for discharging the gas out from the channel in the event that internal pressure exceeding a certain pressure (i.e., abnormal pressure) is applied to the channel; wherein the gas bypass means includes a hole provided to the side wall of the channel, and a sleeve which normally plugs off the hole disposed within the channel. With the pretensioner according to the second embodiment of the present invention, a protrusion protruding into the hole is preferably provided to the portion of the sleeve which corresponds with the hole.
In this case, there is the advantage that not only is there no gas leakage under normal conditions, gas is discharged only under abnormal conditions. In this case, there is the advantage that the gas pressure within the channel readily converges on the protrusion. Also, fitting the protrusion into the hole also acts to fix the sleeve.
The pretensioner according to a third embodiment of the present invention is a pretensioner for rotating the take-up shaft of a seatbelt in the take-up direction in the event of an emergency to provide the belt with pretension, the pretensioner comprising: a gas generator; a driving member accelerated by the gas generated by the gas generator; a path for storing and guiding the driving member; a channel for guiding the gas to the path; means for converting the motion of the accelerated driving member into force for rotating the take-up shaft; and gas bypass means for discharging the gas out from the channel in the event that internal pressure exceeding a certain pressure (i.e., abnormal pressure) is applied to the channel; wherein the gas bypass means includes a tear line (a side wall portion prepared so as to readily tear in the event that abnormal pressure is applied). With the pretensioner according to the third embodiment of the present invention, the gas bypass means may comprise a hole opened in the side wall of the channel, with this hole being plugged off by the material to which the tear line is provided.
With this embodiment, the channel itself has a gas escaping mechanism, so there is the advantage that additional parts are not necessary. In this case, there is the advantage that the gas escaping pressure can be set by the material to which the tear line is provided.
The pretensioner according to a fourth embodiment of the present invention is a pretensioner for rotating the take-up shaft of a seatbelt in the take-up direction in the event of an emergency to provide the belt with pretension, the pretensioner comprising: a gas generator; a driving member accelerated by the gas generated by the gas generator; a path for storing and guiding the driving member; a channel for guiding the gas to the path; means for converting the motion of the accelerated driving member into force for rotating the take-up shaft; and gas bypass means for discharging the gas out from the channel in the event that internal pressure exceeding a certain pressure (i.e., abnormal pressure) is applied to the channel; wherein the gas bypass means includes a keeper for fixing the gas generator at the end portion of the channel, and is configured such that a gap is created between the keeper and channel in the event of abnormal pressure.
Gas is discharged from the gap between the keeper and the channel in the event of abnormal pressure. Such an arrangement has the advantage that addition parts for gas discharge are unnecessary.
With the pretensioner according to the fourth embodiment of the present invention, an arrangement may be employed wherein a hole is opened at the side wall of the keeper and also an elastic material is introduced between the keeper and the gas generator, wherein the hole is normally plugged by the perimeter surface of the gas generator, and wherein the hole is released in the event of abnormal pressure by the elastic member shrinking and the gas generator moving. In this case, there is the advantage that the discharge pressure of the hole can be set according to the type of elastic material.
The pretensioner according to a fifth embodiment of the present invention is a pretensioner for rotating the take-up shaft of a seatbelt in the take-up direction in the event of an emergency to provide the belt with pretension, the pretensioner comprising: a gas generator; a driving member accelerated by the gas generated by the gas generator; a path for storing and guiding the driving member; a channel for guiding the gas to the path; means for converting the motion of the accelerated driving member into force for rotating the take-up shaft; and gas bypass means for discharging the gas out from the channel in the event that internal pressure exceeding a certain pressure (i.e., abnormal pressure) is applied to the channel; wherein the path is a channel and the driving member moves along the inner surface of the channel; and wherein a piston is further provided to the end of the driving member, and a small hole is opened in the side wall of the channel at the position where this piston passes in the initial stage of being accelerated; and wherein the diameter of the small hole is of a size which allows pressure necessary for normal operation to be maintained within the channel and also does not allow an excessive pressure in the event that the movement of the piston is obstructed. Incidentally, the piston can move to the position for discharging the hole, even in the event that the take-up shaft does not rotate.
The fifth embodiment of the present invention is advantageous in that there is no leakage of gas and pressure can be maintained until the initial stage of the piston starting movement.